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Subject: Re: [PATCH v2] xen-blkfront: allow discard-* nodes to be optional
To:     =?UTF-8?Q?Roger_Pau_Monn=c3=a9?= <roger.pau@citrix.com>
Cc:     linux-kernel@vger.kernel.org,
        Boris Ostrovsky <boris.ostrovsky@oracle.com>,
        Juergen Gross <jgross@suse.com>,
        Stefano Stabellini <sstabellini@kernel.org>,
        Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
        Jens Axboe <axboe@kernel.dk>, xen-devel@lists.xenproject.org,
        linux-block@vger.kernel.org,
        Arthur Borsboom <arthurborsboom@gmail.com>
References: <20210119105727.95173-1-roger.pau@citrix.com>
 <CALUcmUkd9Eeau6tC9ZWHbLdvHTYfY34LvK6KKpOOxreYF67Myg@mail.gmail.com>
 <20210120143515.v2vgyhcxrhnnng6r@Air-de-Roger>
From:   Jan Beulich <jbeulich@suse.com>
Message-ID: <83d1aca5-2637-f1f2-3006-69fc6ba76bb4@suse.com>
Date:   Wed, 20 Jan 2021 15:37:57 +0100
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On 20.01.2021 15:35, Roger Pau Monné wrote:
> On Wed, Jan 20, 2021 at 03:23:30PM +0100, Arthur Borsboom wrote:
>> Hi Roger,
>>
>> I have set up a test environment based on Linux 5.11.0-rc4.
>> The patch did not apply clean, so I copied/pasted the patch manually.
>>
>> Without the patch the call trace (as reported) is visible in dmesg.
>> With the patch the call trace in dmesg is gone, but ... (there is always a
>> but) ...
>>
>> Now the discard action returns the following.
>>
>> [arthur@test-arch ~]$ sudo fstrim -v /
>> fstrim: /: the discard operation is not supported
>>
>> It might be correct, but of course I was hoping the Xen VM guest would pass
>> on the discard request to the block device in the Xen VM host, which is a
>> disk partition.
>> Any suggestions?
> 
> Hm, that's not what I did see on my testing, the operation worked OK,
> and that's what I would expect to happen in your case also, since I
> know the xenstore keys.

Does discard work on partitions (and not just on entire disks)?
It's been a while since I last had anything to do with this code,
so I may well misremember.

Jan